That's great news. I love Nepalese food. The first restaurant I regularly took myself to on my own, a quarter of a century ago, was the appropriately named Great Nepalese on Eversholt Street, opposite Euston Station (and next door to a transvestite shop called Transformation – rich potential for embarrassing bumpings-into). The waiters were former Gurkhas, as waiters at Nepalese restaurants tend to be, and they had a photo on the wall of the surviving Gurkha holders of the Victoria Cross. They served Nepalese coronation rum from a bottle the shape of a kukri (the Gurkha ritual knife): the effect was like punching yourself in the face, but in a good way.

Nepalese food is rich and meaty, as food from the northern end of the subcontinent tends to be, but the heaviness is alleviated by a generous use of herbs and greenery. There is also what the Oxford Companion To Food calls "the Chinese influence mediated through Tibet", which manifests itself particularly in a dumpling known as momo, a heavier, more macho form of steamed pork dim sum. Momo are served at all formal meals in Tibet and if you go to a Nepalese restaurant and don't try them, you're missing out.

There used to be something called a "Good Food Guide restaurant", which meant a Mexican restaurant above a launderette in Ipswich, say, or the front room of someone's house in Wiltshire where you had to order in advance. The formula was for an unpromising, downbeat location with unexpectedly good cooking. Yak Yeti Yak is a version of this: a Nepalese restaurant in a basement below a hair studio in Bath. I defy anybody walking past instantly to think, "Ooh, I fancy that."

Look twice, though, and you notice there are quite a few happy customers already ensconced in Yak Yeti Yak. (Terrible name. I suppose it's a pun on yakkety-yak, but still – it combines two things you don't want to eat, one of which doesn't exist.) It's clearly a big success locally, and is bigger than it looks, with several rooms, a courtyard and a space for traditional seating at low tables with cushions on the floor.

The reasons for its success? Naturally, it's rocket science: the food is good, the service efficient and very friendly, and the bill small. The Nepalese classics are present and well-executed, especially a hearty version of momo served with a lightening, delicate hemp seed chutney. Then it's all about the mutton – or, rather, the lamb; maybe slow-cooked mutton would be better with the generous, subtly textured, cumin-heavy spicing, because the lamb was cooked a bit too quickly and erred on the chewy side.

The vegetable dishes were great: musurko dhal – made with red lentils, showed a liberal use of garlic and, I suspect, quite a bit of ghee – had that nicely layered sense of many different spices working in harmony. Chamsur sag was spinach and watercress, stir-fried with fresh herbs and cooked so the veg still had some bite rather than being mushily indistinct – maybe some of that Sino-Tibetan influence was at work there. All in all, the balance of the cooking was just right. I could tell because I wasn't still awake at three in the morning hallucinating, which is what sometimes happens after I've eaten a meal from a kitchen that is secretly caning the ghee.

I was on my own, which brought various happy memories of the Great Nepalese, and also involved a certain amount of eavesdropping, as it always does. The climax of this was when a middle-aged man at a table of two mixed couples very distinctly finished a sentence with the words, "Their greasy little bumholes." The room went quiet, trying to discover what they'd been talking about, but the table of four went to whisper mode, so we never learned. I wish Patsy from Ab Fab had been there.